Skip to main content

Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

See other formats


the nitrate evaporated and the residue employed for the detection of resin
by means of acetic anhydride and sulphuric acid (see General Methods,

The. quantitative determination may be effected by Twitchell's method
(see General Methods, 20).

8. Paraffin Wax and Ceresine.—As a preliminary test, 5 grams of
the wax, about 25 c.c. of semmormal alcoholic potassium hydroxide and
20 c.c. of 95% alcohol are boiled for an hour in a reflux apparatus over a
naked flame : with pure wax the solution is clear, or almost clear, and remains
so when diluted with hot water, but with wax mixed with paraffin wax
or ceresine, the liquid remains turbid, and becomes still more so when diluted
with water.1

A more certain and even quantitative test may be made by Leys'
method2: 10 grams of the wax, 25 c.c. of alcoholic potash. (45 grams
KOH per litre of absolute alcohol) and 50 c.c. of pure benzene are boiled
for 20 minutes in a reflux apparatus on an asbestos card over a naked flame,
50 c.c. of water being then added and the boiling continued, for 10 minutes.
After a short rest, the liquid separates into two layers : an upper, clear,
yellowish one (benzene solution of higher alcohols and hydrocarbons) and
a lower, somewhat opalescent one (aqueous-alcoholic soap solution). As
soon as the separation is sharp, the lower hot liquid is drawn off and replaced
by 50 c.c. of hot water, and the liquid boiled for 10 minutes with a reflux
apparatus. The aqueous solution is then immediately withdrawn and
the benzenic liquid transferred to a tared capsule, the various vessels in
which the operations have been conducted being washed out with hot
benzene3; the solvent is then evaporated on the water-bath and the residue
dried at 100° and weighed. This gives the total weight of higher alcohols
and hydrocarbons contained in .the wax and from this the content of extrane-
ous hydrocarbons may be deduced, knowing that in pure wax the sum of
alcohols and hydrocarbons never exceeds 55% (usually oscillating about

If desired, the hydrocarbons may, according to Leys, be separated
quantitatively from the higher alcohols by means of a mixture of amyl
alcohol and cone, hydrochloric acid, in which the latter dissolve (see original
paper) ; or, as Buchner recommends,* the acetyl number (sea General
Methods, u) of the mixed higher alcohols and hydrocarbons may be deter-
mined and the quantity of the former deduced by taking 122 as the mean
acetyl number of the higher alcohols of the pure wax.

9. Test for Carnauba Wax and Insect or Chinese Wax.—No
special reactions exist for identifying these waxes in beeswax ; when, how-
ever, the presence of other extraneous substances has been excluded and
any stearic acid and resin eliminated as indicated above (6), their presence
may be presumed from increase of the specific gravity, melting point,

1  Werder :   Monit. scient.,  igoi, p.  127.

2  Journ. de Pharm. et Chim., 1912, V, p. 577.

3  Very suitable for this purpose is a special vessel (Boule a decantation chaude)
devised by Leys and consisting of a tapped funnel flattened on one side so that it may
be heated like an ordinary flask.

* Zsitschr, f. offentl. Chem., 1913, p. 447.) 0-926 (15°)